#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_map<int, int>hashi;
        for (auto e : nums)
        {
            hashi[e]++;
        }
        for (auto e : nums)
        {
            if (hashi[e] >= 2) return true;
        }
        return false;
    }
};